Oswaldo Coca

La implementación de medidas basadas en ecosistemas como alternativas de adaptación frente al cambio climático ha cobrado importancia frente a amenazas naturales en zonas costeras. En términos de erosión costera, los arrecifes se consideran una morfología marina que reduce la energía del oleaje al conformar una superficie rugosa en el fondo. Para evaluar la viabilidad de esta alternativa se requiere un contexto geológico, oceanográfico y climatológico, temáticas que abarcan los procesos que condicionan la presencia de dichos ecosistemas. El monitoreo de erosión costera en el departamento de Córdoba permitió identificar el corregimiento de Santander de la Cruz como sitio prioritario para evaluar una alternativa de mitigación basada en ecosistemas. Se generó un modelo batimétrico detallado como base para la identificación de rasgos morfológicos del fondo marino; adicionalmente, se colectaron muestras de sedimento y una muestra de roca para establecer las principales características sedimentológicas del área. En la zona marina al occidente del corregimiento de Santander de la Cruz se identificó una morfología rugosa sobresaliente desde el plano sedimentario, cuyas características indican la presencia de fondos duros. El fondo se caracterizó por presentar sedimentos arenosos de tamaño muy fino a fino que conforman el depósito de playa sumergido con pendiente muy baja, mientras que hacia la zona de influencia marina los sedimentos se caracterizaron por ser de tipo limo a arcillas. Estos depósitos se vieron interrumpidos por la estructura rocosa natural que forma un eje cóncavo de tendencia nororiente-suroccidente, casi paralelo a la línea de costa. Las características geológicas del fondo, representadas en el relieve natural, constituyen una línea base para la implantación de un arrecife artificial, y son referente para la presencia de ecosistemas de fondos duros. Para definir su viabilidad se requiere de análisis detallado del material rocoso, características oceanográficas y bióticas que puedan favorecer el crecimiento del ecosistema.

Customizing environmental assessments to the particularities of the type of environment is crucial for implementing the precautionary principle. This paper uses the SHIELD model (Susceptibility to Human Interventions for Environmental Licensing Determination) in the context of geomorphology for the effective management of coastal environments. This paper describes the customization of the SHIELD model for tropical coastal environments as a way of validating a specific kind of environment. The assessment translates expert knowledge into technical criteria for the environmental control of human interventions through fuzzy logic computations. This assessment identified 21 geomorphological processes across six categories. Moreover, computation of the parameters resulted in a database of susceptibility measures for 4524 interactions. These quantitative results could guide future environmental impact studies of coastal environments, considering licensing instrument requirements. The SHIELD model approach, illustrated here on tropical coastal environments, offers a technical alternative for improving the environmental control of anthropogenic impacts from a geomorphological perspective.

Coastal erosion is a common phenomenon along the world’s coasts. Studying it is complex because such studies must cover large portions of land, and it is necessary to understand the multiple processes that interact in each area, so it is important to recognize regional patterns that allow for defining representativeness in relation to the surrounding dynamics. Spatial statistics can be used in coastal geomorphology to identify and quantify trends in coastal morphodynamics. This study analyzes and interprets the spatio-temporal patterns present in the changes in a shoreline, that is, the processes of erosion and coastal sedimentation in the Pacific and the Colombian Caribbean. The results are derived from the detection of significant changes in the coastline via satellite images. For this study, the shoreline of Colombia was digitized for the years 1986 and 2016, thus obtaining changes in the shoreline at a medium temporal scale. The Global Moran’s Index, Local Moran’s Index and Getis–Ord Index were used to explain the spatial statistics. The Global I Moran values for the Pacific were I = 0.190, z = 31.063 and p = 0.01, and for the Caribbean I = 0.624, z = 74.545 and p = 0.01, which suggests good grouping in the Caribbean and very low grouping for the Pacific. The local indices (Moran’s and Getis–Ord) allowed us to visualize and spatialize the significant points of coastal erosion and sedimentation. According to the results, three conceptual models are herein proposed that relate the indices with the geomorphological characteristics: (a) the greater the geomorphological heterogeneity, the greater the grouping; (b) the greater the geomorphological homogeneity, the lower the degree of clustering; (c) the greater the geomorphological complexity, the lower the degree of clustering. Finally, it is confirmed that coastal erosion and sedimentation processes predominate along low coasts.

The massive explosion by the January 15, 2022 Hunga Tonga-Hunga Ha’apai volcano in Tonga triggered a trans-oceanic tsunami generated by coupled ocean and atmospheric shock waves during the explosion. The tsunami reached first the coast of Tonga, and later many coasts around the world. The shock wave went around the globe, causing sea perturbations as far as the Caribbean and the Mediterranean seas. We present the effects of the January 15, 2022 Tonga tsunami on the Mexican Pacific Coast, Gulf of Mexico, and Mexican Caribbean coast, and discuss the underrated hazard caused by great volcanic explosions, and the role of early tsunami warning systems, in particular in Mexico. The shock wave took about 7.5 h to reach the coast of Mexico, located about 9000 km away from the volcano, and the signal lasted several hours, about 133 h (5.13 days). The shock wave was the only cause for sea alterations on the Gulf of Mexico and Caribbean Sea, while at the Mexican Pacific coast both shock wave and the triggered tsunami by the volcano eruption and collapse affected this coast. The first tsunami waves recorded on the Mexican Pacific coast arrived around 12:35 on January 15, at the Lázaro Cárdenas, Michoacán tide gauge station. The maximum tsunami height exceeded 2 m at the Ensenada, Baja California, and Manzanillo, Colima, tide gauge stations. Most tsunami warning advisories, with two exceptions, reached communities via social media (Twitter and Facebook), but did not clearly state that people must stay away from the shore. We suggest that, although no casualties were reported in Mexico, tsunami warning advisories of far-field tsunamis and those triggered non-seismic sources, such as landslides and volcanic eruptions, should be included and improved to reach coastal communities timely, explaining the associated hazards on the coast.

The coastline throughout the world and Colombia shows a retreat trend, with significant impacts on local communities and ecosystems. To address this problem, it was proposed to include it in Disaster Risk Management, a process-based approach that starts from knowledge to take corrective and prospective measures, being the hazard and vulnerability analysis the main input, and the evaluation of its components relevant for the proposal of alternatives. For this study, the dominance of each of the components of the hazard assessment (occurrence, magnitude and susceptibility) and vulnerability (exposed elements, fragility and lack of resilience) proposed by Coca-Domínguez and Ricaurte-Villota (2019) was analyzed using principal component analysis. The results show that the determining factor of the erosion hazard in the Pacific and the Insular zone is occurrence, while in the Caribbean it is susceptibility, which may be conditioned by the generalized trend of retreat of the Colombian coastline, while in the Caribbean it is explained by the characteristics of the coast. Vulnerability in the Caribbean and the Insular zone is determined by the lack of resilience, and in the Pacific by fragility, explained by the loss of traditional knowledge and ecosystems, moreover of differences in development and occupation between the Caribbean and the Colombian Pacific.